There are many application where it is desirable to reduce the height of a tree to protect the tree from more severe damage, for example being blown down, by reducing the height of the tree. Such systems would be particularly useful to protect the ecology particularly adjacent to creeks where blow down is likely to be detrimental to the fish life in the creek or along hydro-electric lines or at the edges of clear-cuts or in any suitable location where tall trees maybe subjected to relatively high wind forces that may topple the tree and cause significant damage, not just to the tree, but also to its immediate surroundings. Also when fighting forest fires in remote regions it would be desirable to apply equipment to selectively eliminate trees by reducing them to chips.
The concept of clipping the top off a tree is not new, for example, U.S. Pat. No. 3,536,113 issued Oct. 27, 1977 to Southerland, discloses a boom mounted cutting head for tree topping, delimbing and bucking system wherein the delimber and cut off mechanism are supported at the free end of a boom and are moved down the tree to first top the tree and then delimb and buck the tree into sections as the head is lowered.
U.S. Pat. No. 3,576,203 issued Apr. 17, 1971, to Cote, discloses a similar device but wherein a chipper is used in place of the bucking mechanism, the chipper is forced to downwardly onto the top of tree to reduce the tree to chips or shavings. The particular mechanism used includes a delimber coupled to a pencil sharpener-like chipper that reduces a standing tree to chips.
U.S. Pat. No. 5,042,727 issued Aug. 27, 1991 to Plante, discloses a similarly mounted bush wood chipper that incorporates flails in the form of pivotal cutting blades that break the tree, particularly the bush, into a plurality of discrete wood particles (chips) and eliminates the tree to ground level.
In all the above described devices, the cutting or chipping systems require rigid support of the cutting mechanism and thus, a relatively rigid (as opposed to a free slung support) must be used to absorb the torque applied to rotate the cutting head.
It is also known to suspend tree cutting elements from helicopters by various means. One of the earlier devices for heli-transport is shown in U.S. Pat. No. 2,707,008 issued Apr. 26, 1955 to Bannister, wherein a gripping element and a cut off mechanism are separately cable supported from the helicopter. One is to griping element grips the top of a tree while the cut off mechanism is lowered to the base of the tree and cuts the tree at its base. After the tree has been cut off it is lifted above the other trees and carried via the gripping element it to the desired location. Obviously, there will be a problem in lowering the cut off mechanism to the base of the tree in a position to cut off the tree, since it would have to drop down between adjacent trees and be positioned adjacent to the base of the tree to be cut.
In a more recent patent, namely, U.S. Pat. No. 4,662,414 issued May 5, 1987 to Fandrich, there is disclosed a system of cutting off and collecting the tree tops. The cut off system is supported from a helicopter and includes a catch basket to catch the sheered off top and permit it to be transported away via the helicopter, i.e. the whole unit is lowered by the helicopter over the top of the tree, a sheer is activated to cut the top of the tree off, the top topples into a basket and is then carried away. This system is used for gathering cones for replanting and only short lengths can be moved.
U.S. Pat. No. 4,815,263 issued Mar. 20, 1989 to Hartung et al., describes a delimber system that is suspended via a semirigid pole from the bottom of a helicopter and is provided with a plurality of rotating (circular) saws, each blade being substantially parallel to the next and arranged in a substantially vertical plane so that when moved passed tree, the blades cut the branches off along the line formed by the saw blades. Obviously, this system cannot be freely suspended via a cable or the saw blades would tend to rotate around the axis of the cable and their relative positions would not be fixed and the effectiveness of the system would be eliminated.
U.S. Pat. No. 4,984,757 issued Jan. 15, 1991 to Hartung, discloses a particular mounting mechanism for suspending a cut-off device such as a circular saws of U.S. Pat. No. 4,815,263 referred to above and pivot the mounting system into position 90.degree. to the normal cutting positioning i.e. to a substantially horizontal position for landing. It will be apparent that while some cut-off devices will be suitable for eliminating a tree, such mechanisms are generally not practical for cable support from a helicopter and either result in cutting the top of a tree as a whole which could damage the forest floor or requires relatively complicated and heavy mechanism for carrying the tops off and then is limited to short lengths. Nothing has been provided that can be transported to remote areas e.g. by suspension via a cable from a helicopter to chip the tree from the top down to reduce the height of the selected standing tree and distribute suitably sized chips or flakes onto the forest floor.